Authors: Ambarish Gopal Song S Mao Daniel Karlsberg Emily Young Joshua Waggoner Naser Ahmadi Raveen S Pal John Leal Ronald P Karlsberg Matthew J Budoff
Publish Date: 2008/12/03
Volume: 25, Issue: 4, Pages: 405-416
Abstract
Current 64multidetector Computed Tomographic scanners MDCT utilize retrospective overlapping helical acquisition RSOHA which imparts a higher than desired radiation dose Although the radiation burden of computed tomographic angiography CTA can be efficiently reduced by dose modulation and limiting field of view a further decrease in radiation without compromising diagnostic image quality would be indeed very desirable An alternative imaging mode is the axial prospective ECGtriggering acquisition prospective gating This study was done to compare the effective radiation dose and the image quality with two techniques to reduce radiation doses with CTA studies utilizing 64MDCT scanners The study included 149 consecutive patients 48 females and 101 males 64MDCT mean age = 67 ± 11 years 722 male Patients underwent CT coronary angiography using one of three algorithms retrospective triggering with dose modulation prospective triggering with padding step and shoot acquisition with additional adjacent phases and prospective triggering without padding single phase acquisition only Based on body habitus two different voltages were utilized 100 kVp 85 kg or 120 kVp 85 kg Radiation doses and image quality signal to noise ratio was measured for each patient and compared between different acquisition protocols The signal tonoise ratio of the ascending aorta SNRAA was calculated from the mean pixel values of the contrastfilled left ventricular chamber divided by the standard deviation of these pixel values Use of 100 kVp reduced radiation dose 415 using prospective triggering and 396 using retrospective imaging as compared to 120 kVp P 0001 Use of prospective imaging reduced radiation exposure by 826 as compared to retrospective imaging P 0001 Using both prospective imaging and 100 kVp without padding single phase data no other phases obtained radiation dose was reduced by 90 P 0001 In terms of image quality the coefficient of variation of ascending aortic contrast enhancement between kVp of 120 and kVp of 100 was 6 105 95 CI 093–117 and 78 09 95 CI 07–12 at the pulmonary artery The prospective ECGTriggered acquisition and 100 kVp images were of diagnostic quality allowing adequate assessment in all patients CTA using PA and 100 kVp reduced the radiation dose by up to 90 without compromising the image quality
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